Recovery from exercise at varying work loads. Time course of responses of heart rate and systolic intervals.

Abstract

The time course of the recovery period was characterised by non-invasive measurements after 4-minute bicycle exercise at 3 separate (50W, 100W, and 150W) work loads in 10 volunteers in whom the peak responses during exercise of heart rate and systolic time intervals were consistent with previous investigations of comparable subjects. Most responses started immediately to return toward resting control values. Despite rapidly falling post-exercise heart rates, left ventricular ejection times fellfurther from their exercise nadirs for the first 5 to 15 seconds of recovery (depending on load) probably because of diminished stroke volume caused by venous pooling and, probably also, by continued rapid ejection rate. The stroke volume change was indicated by a concomitant precipitous fall in ejection time index, which then stabilised in tandem with the subsequently normal (i.e. discordant) left ventricular ejection time-heart rate relation. For the first 30 seconds, heart ratefellfrom load-related exercise peaks, but at equal slopes of changefor all loads; thereafter, rates of return toward resting control were strictly load-related. Changes in pre-ejection period were determined by changes in isovolumic contraction time; the degree of return toward control of pre-ejection period and isovolumic contraction time from their exercise nadirs was load-dependent throughout recovery; loaddependent differences in their rate of return were pronounced in thefirst 30 seconds. The rates of change in the ejection time index and in the ratio pre-ejection period/left ventricular ejection time (PEPILVET) were virtually independent of load throughout most of recovery.Polygraphic recording of systolic time intervals (STI) has been successfully applied during upright exercise (Miller et al., 1970;Pigott et al., 1971;Lindquist et al., 1973;Lance and Spodick, 1975;Xenakis et al., 1975 (Aronow, 1970;Pouget et al., 1971;McConahay et al., 1972), the time course of changes during the recovery period has not been systematically investigated.We studied the post-exercise recovery period after graded dynamic upright exercise. The purpose of this investigation was to characterise the changes in cardiac dynamics, as expressed by the systolic time index in healthy young men throughout the first 5 minutes of recovery after submaximal exercise on a bicycle ergometer, and to study the effect of different exercise loads on the time course of recovery. Methods (A) SUBJECTSTen young healthy male volunteers, ages 23 to 32 (mean 27 years), were studied. They were all normally active but not trained athletes and had a 958

Heart rate reactivity to laboratory tasks and ambulatory heart rate in daily life.

“…Also, since these subjects did not engage in strenuous exercise during the ambulatory recording period, and heart rate increases elicited by mild and moderate levels of exercise usually return to baseline within seconds after cessation of the physical activity (29), it is likely that heart rates for ambulatory minutes with no measured physical activity were influenced very little by physical activity from preceding active minutes. This does not preclude the possibility that heart rates during "inactive" minutes were influenced by skeletal muscle contractions not associated with leg movement.…”

Left Ventricular Functional Recovery from Exercise in Normals and Patients with Coronary Heart Disease

“…The level of the load, estimated by the duration of exercise, was also significantly lower in the CAD group. However, it has previously been shown that the PEP/LVET ratio, which is a comparable index, is virtually indepen dent of the load of exercise in normals [6], Third, we measured global abnormalities in LV function; since CAD is a segmental dis ease, our data are prone to a type II error.…”

Systolic time intervals and impedance cardiography.

“…The argument that we used a peripheral pulse does not (as we demonstrated) affect the validity of the systolic time interval responses. Moreover, recent work has shown (Nandi and Spodick, 1977) that within the first 15 seconds after the conclusion of bicycle exercise the LVET continues to fall and then begins to rise. Thus, small differences among subjects in the exact timing of a post-exercise recording could produce widely divergent individual responses, impairing the validity of any group mean.…”